OK her is my setup.
Without this forum i couldn't get all the info i needed. So thx for that
The wall mount is screwed on a wooden board to get the necessary distance for the alu l-profiles.
The profiles came with a diffusion cover.
The LEDS are controlled with an arduino nano which is connected to my PC.
I couldn't use RPi because there is (to my knowledge) no possibility to work with 4k-120Hz
I only use the TV as an secondary PC monitor so I opted to use the Windows grabber.
I still need to fix the corners. There is no diffusor so the light is brighter on the corners.